Ever increasing requirements for reducing the size of packaged semiconductor devices has led to the development of several different types of semiconductor packages. As examples of indicative prior art, reference may be had to United States patent identified by U.S. Pat. No. 5,355,283. This patent describes a ball grid array in which one or more vias are formed through a substrate to electrically interconnect conductive leads formed on another surface of the substrate.
Another example is found in United States patent identified by U.S. Pat. No. 5,397,921. This patent describes a grid array package for an integrated circuit. This package has a tape substrate bearing a pattern of conductive leads radially emanating from a die aperture to connect to an area array of pads arranged on the tape perimeter.
Reference may also be had to United States patent identified by U.S. Pat. No. 5,541,450 which describes a ball grid array semiconductor package with a semiconductor die attached to a support substrate within the opening in the substrate. Bond pads on the chip are electrically connected to ball pads on the lower surface of the substrate.
Generally speaking, reduced sizes of semiconductor devices use an inverted die that is directly attached to a substrate to thereby increase the density of external connections that are provided within the perimeter of the package.
The inverted die, when assembled to form a semiconductor package is known in the art as a flip chip semiconductor package, sometimes comprises a flexible and foldable tape substrate with a pattern of runners with corresponding outer portions that are made available for interconnection to, for example, a printed circuit board. The inverted die is mounted to the substrate and the runners are connected, typically by solder, to pads on the die. With this package a relatively high density of runners can be formed on the flexible and foldable tape substrate to provide a higher density of external connections. The flip chip semiconductor package with the flexible and foldable tape substrate is becoming a popular alternative to the conventional more rigid substrate packages.
Currently, flip chip semiconductor packages are manufactured such that after the die is mounted to the flexible substrate to form an assembly. The assembly is preheated then an underfill material is dispensed onto the assembly into a gap between the substrate and die.
Unfortunately, the increasing requirements for reducing the size of packaged semiconductor devices cannot always be adequately met by the prior art. For instance, when considering flip chip packages using flexible and foldable tape substrates, the runners that couple electrodes of the die to ball grid array connectors can make the perimeter mounting area of the package unsuitably large. If the length of the runners were decreased then this would reduced the size of the mounting area, however the runners must have sufficient length so as to provide interconnects between the pattern of external die electrodes and the ball grid array connectors. Further, conventional flip chip packages using flexible and foldable tape substrates do not always adequately provide enough rigidity to allow for reducing stress that may occur on the ball grid array connectors. It would also be beneficial if the prior art packages had a means of physically protecting the die, without the need for a moulded housing, and it would be useful to have an integral radio frequency shield for providing protection when such packages are subject to electro magnetic waves.